Summary The Beaver Air Services Ltd. Piper Navajo PA31-310, serial No. 31-7612107, was departing Pukatawagan at night, on a visual flight rules (VFR) company flight notification to The Pas, Manitoba. The pilot boarded the six passengers and a small amount of hand luggage. Shortly after engine start, the pilot configured the aircraft with 15 degrees of flap, which is normally used for a short field take-off, and backtracked to the threshold of runway 15. The aircraft accelerated normally and the pilot rotated at 85 mph. Immediately after the aircraft became airborne, the left wing dropped sharply. The pilot levelled the wings; however, the aircraft was now off to the side of the runway, and the pilot lost sight of the runway lights. He noticed the left engine surging and decided to carry out an engine failure procedure. He moved the landing gear lever to the UP position and, concerned about rising terrain to the left of the runway, pulled back on the control column while maintaining a wings-level attitude. The aircraft descended rapidly into the terrain to the left of the runway, struck the ground in a nose-high attitude, and slid about 150 metres through deep snow. The aircraft came to rest about 100 metres to the left of the departure end of the runway. One passenger sustained a back injury. Ce rapport est galement disponible en franais. Other Factual Information The runway at Pukatawagan is 2,850 feet long. There is a downslope towards the departure end of runway 15. At the departure end of runway 15 there is a deep gully, after which the terrain immediately rises about 100-125 feet. This rise in elevation occurs directly in line with the runway, about 600 feet past the end of it. To the left of the runway, across the gully, the terrain also rises quickly about 100 feet. The terrain causes turbulence off the end of runway 15, particularly in the warmer months or when there is strong wind. Because of the rising terrain off the end of runway 15, the accepted practice for company pilots was to use a short field take-off procedure for the Navajo on this runway. The short field take-off procedure is authorized in the PA31-310 Approved Flight Manual (AFM). The pilot reported that there was a high overcast ceiling with about six miles visibility in light snow at Pukatawagan. The wind was about five knots from the south, and favoured take-off on runway 15. These conditions were consistent with reports from other aerodromes in the area and from another company pilot awaiting take-off on the taxiway about halfway along the runway. The take-off was conducted in darkness, and there were no lights on the ground beyond the end of the runway. The company pilot waiting on the taxiway observed that the occurrence aircraft crossed the mid-point of the runway at a higher-than-normal altitude. After the aircraft passed his position, he observed it to descend rapidly and crash. Several occupants on the occurrence aircraft reported hearing a warning horn after take-off. The pilot completed his initial flight training in 1992 and subsequently gained experience with several small aviation companies. He obtained a commercial pilot licence with a multi-engine land and sea aeroplane endorsement, and an instrument rating in 1994. Prior to joining Beaver Air Services, the pilot had accumulated approximately 1,400 hours total flight time, with approximately 900 hours on multi-engine aircraft, primarily the Britten Norman Islander. The pilot completed his Navajo training with Beaver Air Services and flew a successful pilot proficiency check (PPC) with a Transport Canada inspector on 21 November 1996. The training and the PPC were completed in a Piper PA31-350, Chieftain. For the purposes of pilot proficiency, the PA31-310 and PA31-350 are grouped together and the PPC is valid in either model. At the time of the occurrence, the pilot's experience on the PA31, both the 310 and 350 combined, was about 70 hours and he was qualified to fly the aircraft single-pilot IFR. He had completed his aviation medical in July 1996. The pilot indicated that his decision to continue with the take-off, following his detection of an engine anomaly, was primarily based on the inadequate runway length on which to land and the rugged terrain under the flight path. The pilot indicated that he did not have to use a significant amount of rudder to stop the aircraft from yawing. He reacted to the engine emergency immediately by cycling the landing gear up to reduce drag. The pilot was concerned about the aircraft's proximity to rising terrain and pulled back on the control yoke. He did not try to establish an airspeed or aircraft attitude and had no recollection of aircraft attitude or airspeeds during the emergency other than the rotation speed of 85 mph. He maintained full back pressure on the yoke until he heard the stall warning horn. He relaxed some back pressure, but the aircraft struck the ground before he could take any other action. The aircraft was examined after the occurrence, and no faults with the airframe or fuel delivery system could be found. The fuel was clean, bright, and free from contamination or suspended ice particles. The left engine was removed and examined in the TSB regional facility. The examination revealed no discrepancies except for two loose clamps on the turbocharger compressor discharge housing duct. Technical records indicated that the exhaust transition assembly on both engines had been replaced about three weeks prior to the accident, necessitating the loosening of the two clamps. The left engine was mounted in a test cell and fitted with a fixed pitch test club propeller. The engine turbocharger and fuel systems were left intact and run as is. The clamps on the turbocharger compressor discharge housing duct were left loose. The engine was primed and started on the second attempt. The engine was run at a low power setting and was brought up to normal operating temperatures. A magneto check was done and normal rpm drops were experienced. The engine was then run to 2,000 rpm and a fuel flow check confirmed normal pressure and flow. The engine was brought up to 2,575 rpm to simulate take-off power. As the engine reached 2,575 rpm, there was a sudden drop of 500 rpm in engine speed and a drop of five inches of manifold pressure. The engine surged momentarily and then regained rpm. Several further attempts were made to reproduce the sudden engine surge; however, none were successful. Subsequently, the engine ran normally at 2,575 rpm with a normal turbocharger boost pressure of 39 inches manifold pressure with the turbocharger compressor discharge housing duct clamps left loose. Because of safety requirements, it was not feasible to simulate an instantaneous air leakage at the duct clamps during the test run. The aircraft engines are equipped with compressor bypass doors on the induction housings. The AFM indicates that in the event of a turbocharger compressor failure, the engine will automatically revert to normally aspirated operation, or approximately 75% of normal rated power.